Packing containers for food products in liquid or semi-liquid form, e.g. milk, soups or the like are manufactured generally from laminated, flexible material which comprises layers of paper and thermoplastics. A known packing container is formed from a laminated web, during its advance through the packing machine, which successively converts it to tubular shape. During the movement of the tube substantially downwards through the packing machine the contents are delivered via a delivery pipe extending into the tube. The continuously moving tube is pressed together at equally spaced intervals with the help of co-operating, reciprocating processing jaws situated at the lower end of the tube, so that transverse flattened zones result wherein the walls of the material tube are sealed to each other in a liquid-tight manner. The tube is thus converted to a coherent band of substantially cushion-shaped packing containers filled with contents. These are separated by means of cuts through the transverse sealing zones whereupon a final shaping process takes place to impart the desired, e.g. parallelepipedic, shape to the packing container.
The delivery of liquid contents which are free of solid particles can take place without interruptions in the manufacture of packing containers in the manner described above, since the sealing together of opposite walls of the packing material tube can be done without hindrance by the liquid. However, solid particles (bits of fruit, beans, asparagus etc.) have to be delivered in such a manner that they do not get caught or in some other manner prevent or impair the transverse sealing of the packing material tube. A preferred prior method to make this possible is to separate the liquid and the solid parts of the contents in advance and to deliver the solid particles (preferably blended with a certain amount of liquid) in the form of metered portions which are delivered to the tube in rhythm with the repeated transverse flattening of the tube. In this manner a metered amount of solid particles can be delivered as soon as a transverse sealing has been completed, whereupon the, continuous flow of liquid contents is preferably to fill the package to the desired volume before the next flattening will take place.
The delivery of the "solid" part of the contents (this designation will be used in the following description and claims for the part of the contents which includes solid particles in the form of fruit pulp, beans etc. blended with a greater or smaller amount of liquid) in the form of portions of a predetermined size is carried out with the help of a metering pump which feeds out from a storage container the solid part of the contents in portions in the delivery pipe to the packing material tube. Owing to the relatively great distance between the metering pump and the lower open end of the filling pipe, a number of portions will "be on the way" in the filling pipe during the continuous manufacture of packing containers. This means that the feeding out of the solid part of the contents at the lower end of the delivery pipe will be relatively uncertain inasmuch as the contents may stop in the pipe outlet or be pressed out too early so that the accuracy of volume as well as the synchronization with the repeated transverse flattening of the packing material tube will be unsatisfactory. Thus the danger of an incorrect amount of solid particles finding its way into the finished packing container is increased, and it cannot be wholly ruled out that the particles of contents may become stuck between the walls of the packing material tube in connection with the transverse sealing work.
In order to avoid this danger is has been proposed previously to provide the lower end of the filling pipe intended for solid particles with some form of valve which is opened and shut in rhythm with the rate of operation of the packing machine, that is to say in rhythm with the transverse sealings of the packing material tube. Although it is possible, of course, to place a conventional disc valve at the bottom end of the filling pipe and manoeuver the same by means of a spindle or a similar manoeuvring element extending vertically upwards through the filling pipe, this is a solution which should be avoided, if possible, because the number of parts in contact with the contents are increased which implies difficulties in the cleaning sterilizing of the machine.
It is a requirement, therefore, to provide a valve arrangement which has few movable elements and which can be placed at the lower end of the filling pipe and be made to open and shut for the contents containing solid particles in rhythm with the working stroke of the metering pump.
It is a further requirement to provide a valve arrangement of the abovementioned type by means of which the solid part of the contents can be proportioned out in such a manner that the desired amount of contents flows out at the desired instant without isolated particles of contents being delayed or getting stuck in such a manner that they interfere with the subsequent transverse sealing of the packing material tube.